Bandgap voltage reference circuits are well known and widely used in the art for providing an output voltage of 1.2 volts or greater that is substantially independent of temperature. The output voltage has a substantially zero temperature coefficient and is produced by summing together two voltages such that one of the voltages has a positive temperature coefficient while the other has a negative temperature coefficient.
Typically, the positive temperature coefficient is produced by using first and second bipolar transistors operating at different current densities such that the first bipolar transistor is operating at a lower current density than the second bipolar transistor. This amplified positive temperature coefficient voltage is then combined in series with the V.sub.BE voltage of a third bipolar transistor which inherently has a negative temperature coefficient such that a composite output voltage having a very low or substantially zero temperature coefficient is provided.
It would desirable to provide a bandgap voltage in low voltage submicron CMOS technology. However, most CMOS bandgap circuits are manufactured utilizing 5 volt CMOS technology. Moreover, many bandgap circuits provide a differential bandgap reference voltage that is not referenced to any power supply rail. However, in particular applications, such as low voltage submicron CMOS applications, it is desirable to provide a bandgap reference voltage that will operate at reduced power supply voltages and can be referenced to a power supply terminal.
Hence, there exists a need for an improved bandgap circuit utilizing low voltage submicron CMOS technology for providing a bandgap voltage referenced to a power supply terminal.